His paternal great-grandfather was the architect Sir Charles Barry.
He was educated at Winchester College, where he was a commoner, and Royal Military College, Sandhurst.
He was commissioned into the Somerset Light Infantry, his father's regiment, in 1929.He joined the Special Operations Executive in 1941, first as the head of the operations department.
Attached to the planning staff of Eisenhower in November 1942, he was recalled to the SOE in 1943 as Colin Gubbins's chief of staff.